In order to obtain good barrier properties against oxygen many packaging materials for foodstuffs whose quality deteriorates at oxidation such as coffee, dairy products etc comprise one or several barrier layers of an organic and/or inorganic nature. The organic barrier layer may be a film laminated to the other layers or applied to one of the other layers in the laminate in form of a dispersion or a solution or by extrusion coating. The inorganic barrier layer, which typically is a metal layer, may also be provided in form of a film or be applied to one of the other layers in the laminate by deposition, ie by metallisation. In order to minimize the costs of manufacture of the laminate it is preferable to prepare the organic layer from a dispersion or a solution or by extrusion coating and to form an inorganic layer by deposition.
In packagings with printed information or illustrations the printing is often made on the inner face of a transparent outer film to protect the print against damage and to obtain a visually more appealing print. If the inorganic barrier layer in form of a metallisation is applied directly to the printed surface, it will discolour the print. It is known to apply a protecting lacquer such as a polyurethane lacquer to the printed surface before the metallisation to prevent discoloration. As a result, a discoloration of the print is avoided in small metallising thicknesses, but in large metallising thicknesses an unwanted discoloration of the print still occur. The discoloration typically occurs in metallising thicknesses in excess of about 2 Ohm/square (about 200 Angstrom) corresponding to oxygen barrier properties of about 3 cm.sup.3 /m.sup.2 /24 hours. When a higher oxygen barrier is desired without the print being discoloured, a separate film is metallised and subsequently laminated to the printed transparent film, thus increasing the costs of manufacture of the packaging material.
EP-A-0 096 581, U.S. Pat. No. 3,949,114, WO92/01558, WO94/23941 and EP-B1-0 281 893 all disclose laminates comprising an organic barrier layer (typically in form of an EVOH film) as well as an inorganic barrier layer (typically in form of a metallisation) so as to improve the oxygen barrier properties.
Further it is known from U.S. Pat. No. 5,153,074 that improved O.sub.2 barrier properties are obtained by coating a polymer film with EVOH for instance by extrusion coating and subsequently metallise the EVOH coating.
Finally U.S. Pat. No. 4,457,977 and EP-A2-0,340,910 both disclose that an improved O.sub.2 barrier is obtained by coating a polymer film with an organic polymer in form of a dispersion or a solution and subsequently metallise said coating.